The present invention relates to a motor having a stator with an insulator. More particularly, it relates to a motor that can dissipate efficiently the heat from a coil section by accommodating at least parts of an insulator with high heat-conductivity.
Two types of stator have been available in motors or generators depending on ways of winding wires, i.e. one is a distributed coil stator and the other is a concentrated coil stator. The distributed coil stator is this: Wire is wound to stride over at least two slots, where a plurality of slots are formed between teeth, in other words, parts of coil of different phase exists in one coil pitch. On the other hand, the concentrated coil stator is this: Wire is wound on one tooth concentrically in one single phase. This stator can advantageously shorten a coil end, thereby downsizing the motor. The reduced wire-wound-resistor of this stator also reduces copper loss generated by wire-wound-current and wire-wound-resistor. This also advantageously produces high efficiency.
A synchronous motor, different from an inductance motor in which a rotor incurs secondary copper loss, dissipates efficiently the heat from stator coils, so that a rated output can be increased. As a result, the synchronous motor achieves high efficiency and a long service life free from adverse influence by heat.
Several cooling methods have been available; dissipating fins on a frame arranged around the stator rim to cool substantially the surface area, a forced cooling system by fan, a liquid cooling system through a cooling-liquid-path provided to a frame. Other cooling systems are also available, e.g. cooling directly the core coils in a motor with oil, dissipating the heat inside a motor through a heat-pipe to outside. However, since these methods cool directly the inside of motor, a number of components inevitably increases, which makes the motor-structure complicated, and thus produces another problem such as maintaining the reliability.
The coilxe2x80x94a heat sourcexe2x80x94is electrically insulated on its surface so that the coil can carry electric current. An insulator or an insulating paper is disposed between the coil and an iron core made of electromagnetic steel sheets in order to prevent the coil from being peeled off its sheath or broken by the edges of the iron core when the wires are coiled. The insulating paper, in general, uses aramid paper. The discussion above describes general structures of the motor-coil.
These insulator and insulating paper are electrical insulating material and at the same time, they are heat insulators and thus block heat conduction. For instance, the aramid paper""s heat conductivity is as low as ca. 0.14W/mK.
An instance is available where highly heat-conductive resin is disposed between the coil and frame to dissipate efficiently the heat from the motor. Indeed, this arrangement increases heat-dissipation-efficiency, but it also increases the motor""s weight. This becomes a critical problem particularly in the motor for an electric-vehicle, because this motor needs to be downsized and demands a greater output at higher efficiency. Further, this arrangement requires equipment and process for potting the resin, and reliability should be reserved in order to avoid shorting due to electrical breakdown of coils depending on the pressure or temperature at the resin potting.
If the material of an insulator is changed to the higher heat-conductive material, the following problem is revealed: In a process of winding a wire on a core, the wire needs some tension, otherwise, the wire becomes loose, and the wire could not be wound correctly within a slot. The insulator has strength bearable at least this tension. On the other hand, an electrical insulator of high heat conductivityxe2x80x94silicone rubber or synthetic resin containing aluminum oxide of excellent heat-conductivity is well knownxe2x80x94is soft and fragile and thus has poor strength not to be an insulator for the coil.
The present invention addresses the problems discussed above and aims to provide a motor that can dissipate the heat generated by a coil.
The motor of the present invention includes a stator formed by combining stator members in an annular shape. The stator members comprise the following elements:
(a) a core segment formed of laminated electromagnetic steel sheets;
(b) an electrical insulator covering the core segment; and
(c) a coil wound on a tooth of the core segment via the insulator. At least a part of the insulator touching at the coil is an insulating resin of high heat-conductivity.
Since a part of the insulator is highly heat-conductive, material of the other parts of the insulator can be selected arbitrarily. Thus the insulator can be strengthened while it increases the heat conductivity between the core segment and the coil.
Another motor of the present invention includes stator iron core formed of laminated electromagnetic steel sheets, and this motor comprises the following elements:
a sheet of highly heat-conductive insulator disposed on the laminated-face of the slot of the stator iron core; and
coils wound in slots via the sheet of highly heat-conductive insulator.
This structure disposes the sheet of highly heat-conductive insulator between the stator iron core and the coils, so that the heat from the coils travels to the stator iron core with ease. As a result, the motor can dissipate efficiently the heat.